Floating platform lock-down mechanisms for spooler troughs and doff trucks



May 28, 1963 Filed March 50, 1961 J. G. FISHER 3,091,503

FLOATING PLATFORM LOCK-DOWN MECHANISMS FOR SPOOLER TROUGHS AND DOFFTRUCKS 2 Sheets-Sheet 1 INVENTOR James 62km fwfiez' ATTORNEYS May 28,1963 J. G. FISHER 3,091,503

FLOATING PLATFORM LOCK-DOWN MECHANISMS FOR SPOOLER TROUGHS AND DOFFTRUCKS Filed March 30, 1961 2 Sheets-Sheet 2 m: INVENTOR JaMeJ'fiZQ/Z/zf'iiker ATTORNEYS United States Patent Or 3,091,503 FLOATING PLATFORMLOCK-DGWN MECHA- NISMS FOR SPOOLER TROUGHS AND DOFF TRUCKS James GlennFisher, Box 350, Hartwell, Ga. Filed Mar. 30, 1961, Ser. No. 99,384 11Claims. (Cl. 312-71) This invention relates generally to improvements inbobbin or spooler troughs and doff trucks of a construction in which afloating platform is employed and the invention is directed particularlyto an improved lockdown means for such platform.

In the operation of textile equipment use is made of spooler troughs,doif trucks and like structures having followers or floating bottomsonto which the bobbins or spools and the like are placed and suchfloating bottoms or follower platforms or bottoms are spring supportedso that as the load in the truck receptacle is lightened the platformwill rise and maintain the articles in position conveniently close tothe open top of the receptacle to enable an operator to remove thearticles without diificulty and without causing unnecessary tiredness.Such follower bottoms or platforms, or floating platforms, are actuatedby relatively heavy springs since it is necessary that the springs besufliciently strong to lift the load when the truck is fully loaded.Consequently when the truck is being filled it is necessary for someoneto hold the platform down while the filling operation is being carriedout.

In my prior application Serial No. 659,402, filed May 15, 1957, nowPatent No. 2,980,481, there is shown a latching or hold-down means forthe follower platform together with a means for manually releasing theholddown from the exterior of the receptacle.

It is a particular object of the present invention to provide ahold-down means wherein a novel construction is provided which enablesan operator to release the platform so that it may be elevated whendesired, without having to manipulate any parts located exteriorly ofthe receptacle.

It is another object of the present invention to provide in a hold-downmechanism of the character above stated, a novel arrangement wherebyrelease of the platform or inactivation of the hold-down means can beeffected by applying a certain amount of downward pressure to theplatform sufficient to force the platform downwardly beyond the latchedor secured position.

A further and more specific object of the invention is to provide in astructure of the character described and in association with a springactuated floating platform, a hold-down mechanism designed to secure theplatform in more than one lowered elevation and having associatedtherewith a novel release means whereby a pivotally mounted latch iscaused to leave 'or become disengaged from the keeper upon thedepression of the platform beyond its lowermost secured position and toguide the latch past the keeper means upon subsequent release of theplatform when the elevating springs take over to return the platform toits fully raised position.

The invention broadly contemplates the provision of a floating platformstructure adapted to be installed as a removable unit in a spooler boxor doif box and comprising a bottom frame resting upon bottom formingmeans 3,091,503 Patented May 28, 1963 ice in the box or receptacle, aplatform above the bottom frame and elevating springs between the bottomframe and the platform and constantly urging the platform upwardly.Stabilizing means interposed between the bottom frame and the platformconstitutes a pair of toggle arm units, one arm of each unit beingfixedly but pivotally attached to the underside of the platform at oneend and the other arm of such unit being fixedly but pivotally attachedto the bottom frame, the other ends of the two arms being slidablycoupled respectively with the platform and the bottom frame.

A latch element pivotally operatively coupled with the platform throughthe medium of two oppositely positioned arms of the toggle units isdesigned to slide forwardly and backwardly with the up and downmovements of the platform and with respect to a keeper. Such keeper isdesigned to receive and hold the latch element in two locationsrepresenting two different elevations or levels for the platform.

Means is provided whereby the latch will be detached from the keeperupon depression of the platform beyond its lowermost latched or securedposition and then guided back past the keeper when the downwardlyapplied pressure is removed from the platform after release of the latchfrom the keeper, permitting the platform supporting springs to thenreelevate the platform.

The invention will be best understood from a consideration of thefollowing detailed description taken in connection with the accompanyingdrawings forming a part of this specification with the understanding,however, that the invention is not confined to a strict conformity withthe showing of the drawings but may be changed or modified so long assuch changes or modifications mark no material departure from thesalient features of the invention as defined by the appended claims.

In the drawings:

FIG. 1 is a view in front elevation of a spooler truck in which aportion of the front wall is broken away to show the improved hold-downmechanism of the present invention and also illustrating the floatingplatform in elevated position.

FIG. 2 is a longitudinal sectional view through the lower portion of thespooler box or receptacle and illustrating the platform in its lowestlock-down position.

FIG. 3 is a vertical transverse section taken substantially on the line33 of FIG. 1.

FIG. 4 is a sectional view on an enlarged scale and taken in ahorizontal plane through the hold-down end of the truck box showing thehold-down mechanism in top plan and operative for securing the platformin an incompletely lowered position.

FIG. 5 is a sectional view taken in .a vertical plane substantially onthe line 55 of FIG. 4.

FIG. 6 is a sectional View taken in a vertical plane similar to FIG. 5but showing the hold-down mechanism operative for maintaining theplatform in the lowest secured position thereof.

FIG. 7 is a detail section taken substantially on the line 7-7 of FIG.5.

FIG. 8 is a sectional detail illustrating the mounting for the latchelevator finger.

Referring now more particularly to the drawings, the numeral 10generally designates a truck receptacle of a type used in the handlingof spindles or packages and designed to be placed by the side of aspooler whereby an operator can doif into the same.

While one type of truck is here shown, it is to be understood that theinvention hereinafter particularly described is not limited to use withthe doff truck here shown but may be used in any receptacle included inthe category of textile apparatus.

The wheel supported receptacle, generally designated 10, comprises thefront and back walls 12 and 14 respectively and end walls 16. The frontwall 12 has an upper inwardly sloping portion 12 which permits thepositioning of the truck against the front or breast of .a spoolermachine.

As shown the receptacle has a top opening 18 and in the bottom partthereof the numeral 20 generally designates a bottom forming means forthe truck, which bottom forming means is here illustrated as beingcomprised of an open frame having the longitudinal side angle bars 22and the transverse end angle bars 24. As shown the angle bars of thefloor forming means are disposed so as to have one web or angle portionextending horizontally inwardly to provide a support for thehereina'fterdescribed floating support means. Thus it will be seen that the bottomforming means provides a central opening 26 in the bottom of thereceptacle which prevents the accumulation of lint in the bottom of thereceptacle. However, it is to be understood that while the bottomforming means has been shown and described as an open frame thereceptacle may be provided with a continuous floor or bottom upon whichthe floating support means may rest.

The truck structure also includes suitable supporting casters or wheelsas illustrated and it is preferred that there be two wheels'adjacent toone end of the truck and spaced apart transversely thereof, forcooperation with a single wheel rearwardly of the pair of wheels andalong the longitudinal center of the truck.

Thetwo laterally spaced wheels are designated 28 and these may besecured to a suitable carrying bar 30 disposed across the floor formingmeans 20 and secured to the undersides of the horizontal flange portionsof the side angle'bars 22.

The single centrally positionedwheel is designated 32 and this also maybe secured to' a carrying bar 34 dis posed across the frame 20 andsecured to the side angle bars thereof.

While-the central or trailing caster wheel 32 has not been shown as aswivel caster, itis to be understood that it may be made in this form ifdesired.

The floating support means is generally designated 36 and is preferablyso constructed, as here illustrated, that itmay be readily removed fromthe receptacle if necessary.

The floating support means 36 comprises a base frame which is generallydesignated 38, a follower platform 40 and two toggle units between thebase frame and the platform, each toggle unit being generally designated42.

The-base frame 38'and the platform 40 are also connected together bysuitable expansion springs, two of which are here illustrated and eachbeing generally designated 44. The base frame 38 is formed in part ofangle iron material and comprises the longitudinal angle iron side bars46-and the transverse'flat end bars 48 and the angle bars 46 arepositioned to have one flange 46a disposed horizontally and extendinginwardly and the other flange 46b extending vertically.

The lower ends of the springs 44 are suitably supported upon thehorizontal inwardly extending flanges 46a of the angle bars 46 either byresting directly upon the flanges or they may be supported upon asuitable plate, not illustrated, which'might be disposed across the baseframe and rest at its ends upon the horizontal flanges of the bars 46.

Each toggle unit comprises two crossed bars 50 which are pivotallycoupled'together intermediate their ends as indicated at 51". One of thetwo bars is pivotally attached as at 52 to the underside of the platform40 at the rear end thereof and the other bar 50 of the same unit ispivotally attached as at 53 to the rear end of the base frame againstthe inner side of the horizontal bar or rail 46. The other end of thebar 50 of each unit which is attached to the base frame extends upwardlyand forwardly and carries a guide pin 54 which is positioned for slidingmovement in a long guide slot 55 formed in a suitable plate for flange56 secured to and depending from the underside of the platform 40adjacent to the forward end of the latter. The forward end of the bar 50of each toggle unit, which is pivotally attached at 52 to the platform,extends downwardly and forwardly and carries a guide pin 57 which hassliding engagement in a guide slot 58 formed through the vertical flange46b of the adjacent side angle bar 46 of the base frame as is mostclearly illustrated in FIGS. 1 and 2.

The two toggle units function to maintain the platform horizontally inits upward and downward movements and in order to strengthen andrigidify the toggle units a transverse brace bar 59 is secured acrossthe space between and at its ends to the innermost bars 50 of the twotoggle units as is most clearly seen in FIG. 3.

The novel hold-down or latch-down mechanism of the present invention isdesigned to function automatically to secure the platform at at leasttwo lowered elevations and to release the platform so that it may bereturned to its fully raised position by the springs 44 when theplatform is pressed downwardly beyond its lowest secured or latchedelevation.

The hold-down mechanism comprises a crock shaft 60 which extendstransversely of and between the lower forward ends of the innermosttoggle bars 50 of the two toggle units as shown in FIG. 4 and the endsof this rock shaft are rotatably supported in bearing sockets 61-carried by the two inner bars 50 of the toggle units. Secured at one endto the rock shaft 60, as at 6 2, is an arm 63 which at its opposite andforward end is secured as at 64, by welding or any other suitablemanner, to the medial portion of a transversely disposed latch element65, here shown as being in the form of a long pin which is ofsufl'icient length to span the space between the side bars 46 of thebase frame andrest at its ends during certain periods in the operationof the mechanism upon the horizontal inwardly projecting flanges 46a ofthe sidebars 46, as shown in FIG. 3.

Secured to the horizontal inwardly extending flange portion 46a of eachangle bar 46, adjacent to the forward end of the bar is an upstandingflange 66 which is spaced inwardly slightly from the free inner edge ofthe flange as clearly shown in FIGS. 7 and 8, so as to provide a portionof the flange to function as a guide track for the movement therealongof an end of the latch elementpin 65, as hereinafter described. Thisflange 66 is also spaced inwardly slightly from the vertical flange 46bof the angle bar 46 to provide space for the movement of the lowerend ofthe adjacent toggle bar 50.

Each of the flanges 66 has secured along its top edge or is formedintegral with an inwardly projecting hori zontal plate 68 which projectsinwardly beyond the inner edge of the horizontal flange of the angle bar46 as is also clearly'shown in FIGS. 7 and 8. This plate 68, the flange66 and the track portion 67 of the angle bar flange forming a guidechannel 6 9 for the adjacent end of the latch element pin 65 in therelease action of the mechanism.

Each of the two oppositely positioned plates 68 supports on its topsurface and adjacent to its inner edge; an upstanding keeper plate 702Each of these keeper plates has a forwardly and downwardly inclined edge71 and an upwardly opening notch 72 immediately therebehind, the notch72 having a substantially vertical forward edge 73 and an upwardly andrearwardly inclined edge 74. Each of the plates has a rear downwardlyandforwardly inclined edge 75 which terminate-s at the bottom end slightlyforwardly of the rear-most end of the plate 68, thus forming a restsurface 76 which corresponds in function to the notch 72, as will becomeapparent in the hereinafter set forth description of the operation ofthe mechanism.

The rearward ends of the flanges and plates 66 and 68 are set forwardlyof or spaced forwardly from the inner side of the transverse bar 48 ofthe base frame, thus forming a recess 77, the top of which lies belowthe top edge of the bar 48 and forms a part of the guide channel forreceiving the ends of the pin 65.

The transverse bar 48 has secured thereto an inwardly projectingdeflector flange 78 which is in a plane above the top of the rear end ofthe plates 68 and overlies the upper part of the recess 77.

The function of this deflector plate 7 8 will become apparent in thehereinafter set forth description of the operation of the mechanism.

At least one of the latch plates 70 has secured thereto and projectinglaterally from the outer side thereof a pivot pin 7 9. This pin isdisposed below and slightly forwardly of the notch 72 and passes throughthe sleeve portion 80 of the latch deflector finger or elevator 81 whichextends forwardly and downwardly and is beveled on its underside toprovide a sharp edge 82 which rests upon the surface flange 46a of theadjacent angle bar 46.

The floating support means rests upon the bottom forming means of thereceptacle and this is effected by the provision of forwardly andrearwardly located transverse flat bars 83 which underlie the flanges46a of the angle bars 46 and rest at their ends upon the horizontalflanges of the angle bars 26.

In the operation of the hold-down or latching mechanism of the presentinvention it will be seen upon reference to FIG. 1 that when theplatform is in the fully raised position the latch element will bedisposed at a substantial distance forwardly of the keeper elements andof the lower end of the latch deflector or elevator 81, the latchelement resting atits ends upon the horizontal flanges 46a of the anglebars 46.

The latching mechanism is designed so that the platform may have twosecured positions or may be secured at two lowered elevations which areindicated in broken lines in FIG. '1 at x and y. In the lowered positionx the latch element pin 65 will rest at its ends in the notches 72 ofthe transversely spaced keeper elements 70, which notches, of course,are in alignment transversely of the structure and when in the lowestposition y the transversely extending latch pin element 65 will rest onthe supporting surface 76, as shown in FIG. 6, so as to hold theplatform 40 against upward movement.

In the operation of latching down the platform in either of these twodesignated positions or elevations, when the downward pressure isapplied to the platform the latch pin element 65 will he slid rearwardlyalong the horizontal flanges 46a and upon reaching the deflector orelevator 81 the element 65 will have one end forced upwardly along therearwardly and upwardly inclined surface of the deflector.

It will be seen upon referring to FIGS. 5 and 6 that the plane of thetop surface of the deflector intersects the plane of the inclinedsurface 71 of the keeper elements and accordingly the ends of the latchpin element will be caused to ride onto these surfaces 71 and continueto move upwardly until it rides over the top of the first point 71:: ofthe keeper to drop into the notch 72. This will effect holding of theplatform at the elevation x.

Further downward pressure applied to the platform will cause the ends ofthe keeper element pin 65 to ride up on the surfaces 74- of the keepersand over the point 74a to drop down behind the rearwardly inclinedsurface 75 onto the supporting surface 76. While the supporting surface76 and the edge 75 are not in the form of a cutout or a notch similar tothe notch 72, it will be appreciated that they in effect function as anotch as the same function 6 is served, the edge 75 hold-ing the pinagainst reverse movement and the surface 76 acting in the same capacityas the notch 72 to support the pin.

After the receptacle has been loaded and it is desired to release theplatform so that the same can be raised by the springs 44, if themaximum load on the platform is not sufficient to effect its automaticrelease, an operator can bring about this action by exerting additionaldownward pressure to the platform and in doing this the ends of thelatch pin element 65 will be caused to ride rearwardly off of the plates68 into the recesses 77 and then upon releasing the platform to permitthe springs to take over the platform may rise and this is permitted bythe ends of the latch pin element being caused to move forwardly in theguide channels 69.

The latch deflector or elevator member, being pivotally supported asshown will be itself raised or elevated by the end of the latch elementpin pressing against the underside thereof and causing it to rise sothat the pin can be freed to move back along the flanges 46a.

One of the arms 50 of a toggle unit is shown equipped with a stop memberin the form of a long pin extending inwardly from the arm at anelevation above and slightly in advance of the shaft 60. This pin orstop member is designated 84 and, as shown in FIG. 4, extends across,and above, the deflector 81. This stop member prevents the deflector 81from being thrown up and over the shaft 60 in the event that theplatform is pushed down with suflicient violence to cause this actionfrom the rapid riding of the latch'element pin 65 up along the surfaces71 of the keepers.

As shown in FIG. 3, the width of the platform 40 is greater than thewidth of the receptacle opening 18. Thus a side portion of the platformextends under the inner side of the sloping front wall portion 12'. Withthis arrangement when the platform is loaded and raised the spools orbobbins will be more or less compacted or compressed in the narrowportion of the opening 18 and consequently the load on the platformcannot be raised to the elevation where any of the spools or bobbinswould spill out from the receptacle.

From the foregoing it will be seen that there is provided by the presentinvention a new and novel lock-down mechanism for a floating platformstructure which can be operated effectively and automatically andwithout requiring the employment of any extraneous or exteriorly locatedmeans for effecting the latching of the mechanism or the unlatchingthereof. In other words, the entire lockdown mechanism is contained inthe lower part of the receptacle or truck box and forms a part of thefloating support means for floating support unit so that it is fullyremovable as an element of such unit and to effect removal of thefloating support means with the lock-down mechanism there is nonecessity for removing or disassembling any parts of the structure ordetachment of any parts of the structure from the box.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined in the appended claims, and allchanges that fall within the metes and bounds of the claims, or thatform their functional as well as conjointly cooperative equivalents, aretherefore intended to be embraced by those claims.

I claim:

1. A textile handling apparatus including a receptacle having an opentop, side and end walls and bottom forming means, a floating supportmeans in the receptacle embodying a follower platform and supportingspring means for and constantly urging the platform upwardly, theplatform being movable from a fully elevated position to at least twolowered positions and being securable in each of said lowered positions,a lock-down mechanism for the support means comprising cooperating latchand keeper elements, one element being operatively-coupled with theplatform and the other element being supported by said bottom formingmeans, said elements being adapted to move relatively to one anotherinto a coupled platform securing relationship upon movement of theplatform to a first one of said two lowered positions, means for guidingone of said elements into said coupled relationship with the otherelement while the platform is moving downwardly into said first one ofsaid lowered positions, and means for effecting uncoupling of the latchand keeper elements while the platform is moving downwardly beyond saidfirst one of said lowered positions to the second one of said loweredpositions.

2. A textile handling apparatus including a receptacle having an opentop, side and end Walls and bottom forming means, a floating supportmeans in the receptacle embodying a follower platform and supportingspring means for and constantly urging the platform upwardly, a lockdownmechanism comprising cooperating latch and keeper elements, one elementbeing operatively coupled with the platform and the other element beingsupported by said bottom forming means, a movable latch elementdeflector means adjacent to said keeper element for receiving andelevating said latch element into latching engagement with the keeperelement upon movement of the platform to a predetermined incompletelylowered position, means for shifting said latch element out ofengagement with the keeper element upon further downward movement of theplatform beyond said predetermined position, and means for guiding saidlatch element uninterruptedly along a reverse path of movement past thekeeper element and under said deflector means to permit upward movementof the platform.

3. A textile handling apparatus including a receptacle having an opentop, side and end walls and bottom forming means, a floating supportmeans in the receptacle embodying a follower platform and supportingspring means for and constantly urging the platform upwardly, theplatform being movable downward from a fully elevated position tosuccessive first, second and third lowered elevations, a lock-downmechanism for the support means comprising cooperating latch and keeperelements, one of which elements is operatively coupled to the platformand the other element being supported by the bottom forming means, saidkeeper element comprising a plate having an upwardly directed edgeprovided with a latch part receiving notch and an inclined latchelevating edge at one end leading toward said notch and-a reverselyinclined edge at the opposite end, said latch element being pivotallymounted for up and down swinging movement, said elements being adaptedto be moved relatively to one another upon up and down movement of theplatform, said latch element including a part positioned to ride up onand over the top of said elevating edge and into said .notchupondownward movement of the platform to its first low elevation position,said notch being formed to effect movement of said latch element part toa position of engagement with said. reversely inclined edge uponmovement of the platform to its second low elevation position, and meansfor effecting release of said latch element part upon depression of saidplatform to its third low elevation position.

4. The invention according to claim 3, with a latch deflector pivotallysupported at one end adjacent to one side of said keeper plate forvertical swinging movement and extending downwardly across saidelevating edge of the keeper plate, said latch deflectorreceiving thesaid latch element part upon movement of the latter toward the keeper toraise and guide said part onto said keeper edge, and said keeper elementpart. moving reversely beneath said latch deflector following itsrelease from the keeper element.

5. The invention according to claim 3, wherein the element coupled totheplatform is the latch element, means supporting the said part of thelatch element for sliding movement toward the said elevating edge of thekeeper plate upon downward movement of the platform whereby said latchelement part is caused to ride into said notch at the first said lowelevation position of the platform, said keeper element being disposedat an elevation above the path of sliding movement of the latch elementpart, and there being a guide channel forming means for receiving thelatch element part upon its release from the keeper element and formedto guide the latch element part in a reverse direction past the keeperelement to permit the follower platform to rise.

6. A textile handling apparatus including a receptacle having an opentop, a floating support means in the receptacle embodying a followerplatform, supporting spring means therefor and constantly urging theplatform upwardly, laterally spaced parallel guide bars supported in thelower part of the receptacle and having forward and rear ends andstabilizing toggle units having arms connected between the platform andsaid guide bars with certain of the arms having ends coupled with theforward ends of the guide bars for sliding movement longitudinallythereof in the up and down movements of the platform, the platform beingmovable downward from a fully elevated position to at least two loweredelevations, a lock-down mechanism for the platform adjacent to the saidforward ends of the guide bars and comprising a keeper means embodying akeeper plate extending longitudinally of thebars and having a top edgenotch, means supporting the keeper plate on and at an elevation abovethe guide bars, a latch element pivot ally joined to that end of'atoggle arm which is coupled to a guide bar and having a part slidable onthe adjacent guide bar for movement rearwardly toward the keeper plateby and upon downward movement of the platform, means for swinging thepivoted latch element upward and effecting elevation of said partthereof into the keeper notch upon said rearward movement thereof by andupon movement of the platform to a predetermined one of its loweredelevations, and means operative upon lowering the platform from saidpredetermined one of its elevations for disconnectingthe latch elementpart from the keeper plate notch and lowering such part to an elevationbelow said keeper plate supporting means onto said bar for reversesliding movement thereon past the keeper plate. i

7. The invention according to claim 6, wherein said means for swingingthe pivoted latch element upwardly comprises an elongate deflectorelement pivotally mounted at one end for swinging movement about ahorizontal axis and extending from said end downwardly and forwardlywith respect to and beyond the front end of thekeeper plate and restingat its other end upon the slailbar along which the latch element part isadapted to si e.

8. The invention according to claim 6, wherein said plate extendinglongitudinally of and in vertically spaced relation to theadjacent guidebar, said keeper plate hav- -1ng a rear end edge position for engagementby'said latch element part, said horizontal plate extending rearwardlybeyond said rear end edge of the keeper plate and providing a supportfor said latch element part, said support being adapted to receive thelatch element part upon rearward and gravitational downward movement ofthe part from said notch whereby said part is maintained in holdingengagement with said rear end edge of the keeper plate, the latchelement part being moved from said horizontal plate rearwardly anddownwardly in the operation of said disconnecting means.

9. The invention according to claim 8, with means disposed rearwardly ofsaid keeper plate for guiding the latch element part to position on saidreceiving support.

10'. The invention according to claim 8, wherein said rear end edge ofthe keeper plate inclines upwardly and rearwardly from the supportingplate.

11. The invention according to claim 8, with a deflecting means for thelatch element part disposed in spaced relation with the said rear endedge of the keeper plate at an elevation between the topmost part of thekeeper plate and said horizontal plate and having a for- 5 ward edgedisposed in a vertical plane perpendicular to said bar and in relativelyclose adjacency to a vertical plane common to the rearmost portion ofsaid horizontal plate and parallel to said first plane.

References Cited in the file of this patent UNITED STATES PATENTS HansonJune 6, Robertson Sept. 23, Eurey Sept. 2,

FOREIGN PATENTS Netherlands Aug. 17,

1. A TEXTILE HANDLING APPARATUS INCLUDING A RECEPTACLE HAVING AN OPENTOP, SIDE AND END WALLS AND BOTTOM FORMING MEANS, A FLOATING SUPPORTMEANS IN THE RECEPTACLE EMBODYING A FOLLOWER PLATFORM AND SUPPORTINGSPRING MEANS FORM BEING MOVABLE FROM A FULLY ELEVATED POSITION TO ATLEAST TWO LOWERED POSITIONS AND BEING SECURABLE IN EACH OF SAID LOWEREDPOSITIONS, A LOCK-DOWN MECHANISM FOR THE SUPPORT MEANS COMPRISINGCOOPERATING LATCH AND KEEPER ELEMENTS, ONE ELEMENT BEING OPERATIVELYCOUPLED WITH THE PLATFORM AND THE OTHER ELEMENT BEING SUPPORTED BY SAIDBOTTOM FORMING MEANS, SAID ELEMENTS BEING ADAPTED TO MOVE RELATIVELY TOONE ANOTHER INTO A COUPLED PLATFORM SECURING RELATIONSHIP UPON MOVEMENTOF THE PLATFORM TO A FIRST ONE OF SAID TWO LOWERED POSITIONS, MEANS FORGUIDING ONE OF SAID ELEMENTS INTO SAID COUPLED RELATIONSHIP WITH THEOTHER ELEMENT WHILE THE PLATFORM IS MOVING DOWNWARDLY INTO SAID FIRSTONE OF SAID LOWERED POSITIONS, AND MEANS FOR EFFECTING UNCOUPLING OF THELATCH AND KEEPER ELEMENTS WHILE THE PLATFORM IS MOVING DOWNWARDLY BEYONDSAID FIRST ONE OF SAID LOWERED POSITIONS TO THE SECOND ONE OF SAIDLOWERED POSITIONS.